I'm developing a 1kW hardware prototype of a DC Nanogrid. The standalone DC nanogrid is supplied by a 1kW PV array and a 60V, 150 A battery bank. As there a no standards as such for a residential DC nanaogrid I'm maintaining a DC link voltage of 120V and output of 24V ( for dc applicances). The PV array gives a Vmpp=72V.
I'm using simple topologies for the buck and the boost converters. I've come across a 380V bus voltage ( standard for data centers and telecom applications) as well. But I find it difficult to implement as the min. dc output voltage is 38V ( 0.1(duty ratio)*380= 38V) if I use the conventional buck converter.
Do you think it's advisable to have a DC link voltage of 120V ? I'm attaching a block diagram of my system as well.
I am happy to exchange email about this topic - [email protected]
If the battery is 60V I would think that is what you would want to use for that link.
On way to work with different voltage level in AC and DC is using dc-ac-dc system with a transformer in between. You can easily regulate your ac o dc output by the transformer.
Since you are feeding the load from the 1 kW PV source, it is advisable to eliminate all converters to save energy. I shall suggest a simple way. Keep an appropriate load voltage near the Vmpp of the PV and put a battery, of the same voltage, in between the PV and the load. Connect a rectifier between the PV and the battery to avoid reverse flow of current from battery to PV. You will find a circuit under 'Solar Lantern' in Chapter 9 of the book "Photovoltaic Systems: Analysis and design" by A. K. Mukerjee and Nivedita Thakur, April 2014. Publisher: PHI Learning Delhi. A 1 kW system is too small to have a buck/boost converter and an MPPT.
Thank you all for you reply.
@A.K. Mukerjee- My load voltage should always be 24V because I'll be connecting dc appliances of that voltage rating. As my load keeps changing I need a converter (here boost)to maintain MPPT. To extend the life of the battery I'll also need a bi-directional charge/discharge converter.
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